Self buffs with Wrath of the Diminutive. This spell reflects damage, and has a rune component. It has a 1 minute duration, and if your group fails to do around 20% damage to the NPC before the buff fades, each person in your group will get hit for 150k. If you succeed, your group will be healed.

Wrath of the Diminutive - Large melee and spell rune. Triggers Dissipation of Wrath when it fades due to absorb damage being met, or triggers Punishment of Wrath if the buff fades due to timer expiring.

Once every 5-6 seconds he picks a random player and spins then so their back is facing him. Then, once every 2 ticks or so, if anyones back is turned to him he will stab them for a very high amount of damage.